Out of bounds! Obama falsely accuses McCain of blocking stem-cell research

What happened: Obama is accusing John McCain of blocking stem-cell research, using a charged appeal from the mother of a diabetic child to slam McCain falsely as someone who's blocking a cure.

"Stem-cell research could unlock cures for diabetes, cancer and Alzheimer's, too," says an Obama radio ad that's airing in selected states. "But John McCain has stood in the way. He's opposed stem-cell research. Picked a running mate who's against it. And he's running on a platform even more extreme than George Bush's on this vital research. John McCain doesn't understand that medical research benefiting millions shouldn't be held hostage by the political views of a few."

The ad then hits home with an emotionally charged appeal from a woman who's identified as the mother of a child with diabetes.

"For Maddy and millions of others, stem-cell research can unlock cures," the woman says in the ad. "Barack Obama understands that. But John McCain just doesn't."

He's voted to lift President Bush's restrictions on federal financing and to expand federal financing of stem-cell research. At some political peril, he stood by that stand during the Republican presidential primaries, when it threatened to cost him support from social conservatives.

"Stem-cell research has the potential to give us a better understanding of deadly diseases and spinal cord injuries affecting millions of Americans," McCain said in April 2007 as he voted to support federal financing.

In 2004, he was one of 14 Republicans who signed a letter to Bush urging him to lift restrictions on the research, which they said had the potential "to treat and better understand deadly and disabling diseases and conditions that affect more than 100 million Americans, such as cancer, heart disease, diabetes, Parkinson's, Alzheimer's, multiple sclerosis, spinal cord injury and many others."

"The fact is John McCain has been a champion for stem-cell research, which holds the promise of curing devastating diseases like cancer, diabetes and heart disease," Sen. Arlen Specter, R-Pa., said Tuesday.

"John McCain bucked the majority of our party in standing strong with me in urging the Bush administration to lift restrictions on stem-cell research, and last year voted to overturn the Bush policy."

Penalty: Set Obama's credibility back 15 yards for manhandling the truth.